Apparatus for manufacturing an optical disk substrate by injection molding

Abstract

An apparatus for manufacturing an optical disk substrate having a foreign-substances index of not more than 1x105 mu m2/g, an optical information-storage medium wherein the substrate has an information-recording layer, includes a cylinder with a liner and a screw coated with TiC and TiN.

We claim: 
     
       1. An injection molding apparatus for producing an optical disk substrate having a foreign substances index of not more than 1×10 5  μm 2  /g by injection molding of a non-melted polycarbonate resin with a viscosity average molecular weight of 10,000 to 22,000 at a resin temperature of 50° to 140° C., said apparatus comprising a cylinder having an inner wall with a lining of Co-Ni-Mo-Cr alloy and a screw for plastication of said resin having a surface provided with a double-layer coating of a TiC inner layer and a TiN surface layer; said screw being movable within said cylinder and the resin exhibiting non-adhesiveness for the alloy lining and the double-layer coating during injection molding thereof. 
     
     
       2. The apparatus as claimed in claim 1, wherein said alloy lining has a thickness of from 0.5 to 5 mm and the double-layer coating has a thickness of from 2 to 40 μm. 
     
     
       3. The apparatus as claimed in claim 2, wherein the thickness of the TiC layer is the same as the thickness of the TiN layer. 
     
     
       4. The apparatus as claimed in claim 1, wherein the Co-Ni-Mo-Cr comprises 5 to 8% of Co, 5 to 8% of Ni, 0.1 to 10% of Mo and 1 to 20% of Cr.